Download File

The CVS
Mediastinum and pericardium
Dr. Nabil Khouri MD, MSc, Ph.D
Size & Location of Heart
Average Size of Heart
• 14 cm long
• 9 cm wide
• posterior to sternum
• medial to lungs
• anterior to vertebral column
• base lies beneath 2nd rib
• apex at 5th intercostal space
• lies upon diaphragm
The Location of the Heart within the Thoracic Cavity
Figure 20.2a, b
3rd
4th
 The mediastinum is a broad central partition
that separates the two laterally placed pleural
cavities.
 It extends:
 from the sternum to the bodies of the
vertebrae; and
 from the superior thoracic aperture to the
diaphragm
 It contains the thymus gland, the
pericardial sac, the heart, the trachea,
and the major arteries and veins.
 It also serves as a passageway for structures
such as the esophagus, thoracic duct,
and various components of the
nervous system as they traverse the thorax
on their way to the abdomen.
The
Mediastinum
MEDIASTINUM
•
•
•
•
1. Superior Mediastinum
2. Anterior mediastinum
3. meddle mediastinum
4. posterior mediastinum
The Superior
Mediastinum
Boundaries
Ant: Manubrium sterni
Post: T-1 to T-4
Sides: Mediastinal pleura
Sup: Plane of thoracic inlet
Inferior: Imaginary line joining
sternal angle and lower border
T-4
10
Superior Mediastinum: Contents:
Muscles:
• Sternohyoid
• Sternothyroid
• Longus colli
Thymus: (in childhood &
puberty)
Veins:
• SVC
• Lt & Rt brachiocephalic
veins,
• Lt Sup Intercostal vein
Arteries:
• Arch of Aorta
• Brachiocepalic artery
• Lt Common carotid
• Lt subclavian artery
11
Trachea & Esophagus
Nerves:
• Vagus
• Phrenic
• Cardiac &
• Lt recurrent laryngeal
nerve (b/w trachea &
oesophagus)
Thoracic Duct
Lymph nodes:
• Brachiocephalic,
• Tracheobronchial,
The Thymus gland
 DEVELOPMENT- bilateral 3rd pharyngeal pouches
 EVOLUTION- largest at birth or during infancy increases slightly during 1st
decade of life and decrease thereafter the site of T-cell production, Secrets
Thomasine hormone which promotes the maturation of T cells
 Roughly a bi-lobed structure
 Normal weight- 5 – 50 gm
The Superior Mediastinum
14
SECTION at T-4
15
Sterno-pericardial ligament.
Internal thoracic artery & branches
Anterior Mediastinum-(narrowest)
Boundaries
Ant: Body of sternum
Post: Pericardium
Sides: Mediastinal pleura
Sup: Imaginary plane
Inf:
Diaphragm
17
Middle Mediastinum: Boundaries
?????
Superior:
Inferior:
Posterior:
Anterior:
18
Middle Mediastinum
Contents:
Heart enclosed in pericardium
Arteries: Ascending Aorta,
Pulmonary trunk with its Lt & Rt
branches
Veins: SVC, Termination of
Azygos, Pulmonary veins
Nerves: Phrenic, Deep cardiac
plexus
Bifurcation of Trachea with
two principal bronchi
Tracheobronchial lymph nodes
19
The Heart & the pericardium
Anatomy of the Heart Wall
 Epicardium – covers the outer surface of the heart and is the same as
the visceral pericardium and anchors the heart to the surrounding
structures
 Myocardium – muscular wall of the heart (cardiac muscle cells)
 Endocardium – inner surface of the heart
 Components of the heart wall include (three layers)
 Epicardium – visceral pericardium
 Myocardium – cardiac muscle layer forming the bulk
of the heart
 Endocardium – endothelial layer of the inner
myocardial surface
PERICARDIUM
•The pericardium is supplied by several arteries that are in the area (e.g., the internal
thoracic), and by the phrenic nerves, which contain vasomotor and sensory fibers.
Pericardial pain is felt diffusely behind the sternum but may radiate.
PERICARDIAL LAYER
The Pericardium
•
The fibrous pericardium
• The outermost layer,
• Firmly bound to the central tendon of the diaphragm.
• Extrapericardial fat, which may be visible radiographically, is often found in the angles
between the pericardium and diaphragm on each side.
• The pericardium is attached to the sternum (by the sternopericardial ligaments) and is
adherent to the mediastinal pleura except where the two are separated by the phrenic
nerves.
•
The serous pericardium:
• Is a closed sac, subdivided into
• the parietal layer of which lines the inner surface of the fibrous pericardium and is
reflected onto the heart as the visceral layer, or epicardium. The potential space between
the parietal and visceral layers contains a thin film of fluid and is known as the
pericardial cavity.
•
Because of the manner in which the reflections of the pericardium occur during
development at the arterial and venous ends of the heart, when the pericardial sac is opened
interiorly in the adult it is possible to pass a finger posterior to the aorta and pulmonary
trunk (arterial end of heart) and anterior to the left atrium and superior vena cava (venous
end of heart). This passage is termed the transverse sinus of the pericardium
•
The reflection at the venous end is complicated and occurs as an inverted U along the
pulmonary veins and inferior vena cava: this recess is termed the oblique sinus of the
pericardium.
Superior Vena
Cava
Aorta
Pulmonary
trunk
Pulmonary
Arteries
Inferior Vena
Cava
The Posterior Mediastinum
Boundries:
The anterior boundary of the posterior
mediastinum is the posterior pericardial wall.
The posterior boundary is the anterior surfaces
of the bodies of thoracic vertebrae T5-T12.
Left
Right
Posterior pericardium
 The posterior wall of the
pericardial cavity.
 The heart has been removed,
we will able to see the cut
borders of the major vessels
entering and leaving the
heart.
 The oblique pericardial sinus
is clearly seen within the four
pulmonary veins and inferior
vena cava at this point.
The Esophagus & vagus Nerves
• When the pericardium is
removed,
– The esophagus can seen along with
its plexus derived from the left and
right vagus nerves.
– The left vagus emerges from the
plexus as the anterior vagal trunk
and the right vagus becomes the
posterior vagal trunk as the
esophagus passes through the
diaphragm to enter the abdomen,.
– The branches from the sympathetic
chain can also be seen
• You can also see that the trachea splits
into the right and left primary bronchi
at the level of the junction between the
superior and inferior mediastinum.
• Once the esophagus has been removed,
the thoracic aortan can be seen
• The thoracic aorta starts at the T4T5 junction and extends the full
length of the posterior mediastinum
passing through the aortic hiatus of
the diaphragm into the abdomen.
• The thoracic aorta gives rise to the
posterior inter-costal arteries which
together with the posterior intercostal veins and intercostal nerves to
form the neurovascular bundle that
travels along the inferior border of a
rib.
• It also gives rise to bronchial
branches that enter the root of the
lung to supply the bronchi and lung
tissue in addition to posterior
pericardial arteries
The thoracic aorta
The thoracic duct
Posterior and between the
esophagus and thoracic aorta, you
will find the thoracic duct,
It is a fragile lymphatic duct that
begins in the abdomen as the
cisterna chyli at T4-T5 lumbar
level.
It travels through the superior
mediastinum on its way into the
neck, where it will enter the
venous system at the junction of
the internal jugular and left
subclavian veins.
 Alongside and Posterior to the
thoracic duct, the veins that drain the
walls of the thorax, the azygos and
hemiazygos veins.
 Each of these veins begin in the
abdomen as the ascending lumbar
veins.
 The hemiazygous veins:
 The upper intercostal spaces are
drained by the superior
hemiazygos vein and the lower
the inferior hemiazygos vein.
 These two veins may join as one
hemiazygos vein that passes behind
the thoracic duct to empty into the
azygos vein.
 The two veins may just as
frequently pass into the azygos
separately, forming two hemiazygos
veins.
The azygos and
hemiazygos veins
Splanchnic nerves
 If you reflect or remove the azygos




system of veins, the next structures in
the posterior mediastinum would be the
splanchnic nerves,
Specifically the greater splanchnic
nerves. These nerves are derived from
the sympathetic chains, thoracic
ganglion T5 to T10.
The lesser splanchnic nerves that are
derived from ganglion T10 and T11.
Some anatomist may describe the least
splanchnic that is derived from ganglion
T12.
Remember, according to anatomists, the
sympathetic chain is not part of the
posterior mediastinum.
 The most posterior item
in the posterior
mediastinum is the
anterior longitudinal
ligament which
completely covers the
anterior surfaces of the
bodies of the vertebrae.
 This extends from the
sacral part of the
vertebral column all the
up to the skull.
The sympathetic chain
 You should be able to identify







the
sympathetic ganglion
white communicating ramus
(preganglionic neurons)
gray communicating ramus
(postganglionic neurons)
roots of the splanchnic nerves
(postganglionic neurons)
posterior intercostal veins
posterior intercostal arteries
intercostal nerves